Electric selective signalling systems



Nov. 8, 1955 A. M. HAILEY 2,723,391

ELECTRIC SELECTIVE SIGNALLING SYSTEMS l Filed Nov. l0, 1952 5 Sheets-Sheet 1 Mm Manuf /M/Lf/ Attorney nuv. 1955 A. M. HAILEY 2,723,391

ELECTRIC SELECTIVE SIGNALLING SYSTEMS Filed NOV. 10, 1952 3 Sheets-Sheet 2 Inventor @EMT/475277# 609mg' A ltorney NOV 8, 1955 A. M. HAILEY 2,723,391

ELECTRIC SELECTIVE SIGNALLING SYSTEMS Filed Nov. 10. 1952 3 Sheets-Sheet 3 LMC Inventor f/LETM/WTW muy A ttorney United States Patent O ELECTRIC SELECTIVE SIGNALLING SYSTEMS Albert Martin Hailey, nSiilcup, England, 'assigner to Siemens Brothers la Co. Limited, London, England, a British company i Application November 10, 1952, Serial No. 319,649

Claims priority, application Great Britain December 7, `1.951

4 claims. (c1. 34a- 316) This invention relates to electric selective signalling systems. In its broadest aspect, the invention has in view the provision of improved electrical driving and control arrangements for setting a driven member (for example a shaft or an endless chain or band) from a normal position to any particular one, as signified by a code signal, of a plurality of stopping positions. In a narrower aspect, the invention has in View the provision of an improved electrically-operated changing display indicator arranged to display information (for example gures or letters) signified by code signals. v

In the contemplated improved electrical driving and control arrangements for setting a driven member from a normal position to a stoppingposition signified by a code signal, a control circuit controlling the driving f the driven member has a branch individual to each element of the code employed. Hereinafter, for convenience in description, each such branch of the control circuit will be `termed a control circuit code branch. The contemplated arrangements referred to are such that, at any stopping position before the requisite stopping position is reached (during the setting of the driven member from a normal position to a stopping position signified by a code signal) the condition obtains that one or more control circuit code branches are eective to cause the driving of the driven member to continue. At the requisite stopping position, the condition obtains that no control circuit code branch is effective to cause the driving of the driven member to continue, so that the driven member is stopped in this stopping position. A vcode switching device, Adriven by the driven member, provides in effect a controlling switch in each control circuit code branch. As regards each particular control circuit code branch, the code switching device operates to cause this branch to be open whilst the driven member is at one ormore stopping positions and to be closed whilst the driven member is .at the remaining stopping position or positions. Each control circuit code branch is only connected, to render the branch effective at stopping positions of the driven member at which the branch is closed by the code switching device, if the signal element to which the branch pertains is, in the case of the particular code signal concerned, of a particular character (for example is a mark as `opposed to a space). The arrangements permit the use of a code in which some of the code signals` used are .such that only one of the signal elements is of the particular character referred to, the remaining code signals used f. ICC

being such that twol or more of the signal elements are of the particular character referred to. By reason of the provision of one control circuit code branch per code element, the driven member is enabled in effect to perform a decoding operation without the help of adecoding treeof relay contacts.

According to a main feature of the invention, the code switching device comprises a rotor and xed wipers arranged to make electrical contact with conducting code discs of this rotor, therebeing a conducting code disc for each control circuit code branch (and hence for each element of the code), and each conducting code disc having portions cut away so that a through circuit between this disc and the associated fixed wiper only exists when the rotor is occupying certain positions, and the conducting discs being in permanent electrical connection with one another.

According to another feature of the invention, the driving and controlarrangements are such that the setting of the driven member .from a normal position -to astopping position signified by a code signal is effected in one continuous setting movement, this continuous setting movement being produced by the uninterrupted energisation for the requisite period of the electromagnet of an electromagnetic clutch which serves for coupling the driven member to a primary driving means.

According to a further feature ofthe invention, the driving arrangements are such` that the setting of the driven member from a normal position to a stopping position signified by a code signal is effected in one continuous movement, and the code switching device is coupled to the driven member Vthrough a coupling mechanism which causes each effective .switching movement of the code switching device to take place more rapidly than it would if this device was arranged to be operated in one continuous movement corresponding to the continuous movement of the driven member. The provision of this feature enables undue sparking at the code switching device to be avoided. Such undue sparking might otherwise occur due to the yfact that the device has to open inductive electric circuits. Forms of coupling mechanism which may readily be arranged `to produce a requisite discontinuous movement of the code switching device in response to continuous setting movement of the driven member are a Geneva gear mechanism, and a mechanism in which a cam operates the pawl of apawl and ratchet device.

ln the embodiments of the invention which are especially contemplated, the driven member forms part of an electrically-operated changing display indicator, being for example an endless chain carrying a series of display surfaces to be displayed one at a time.

The code signals need not necessarily be, or correspond to, signals received in code form from a distant station. They may be produced locally solely for the purpose of setting the driven member to diierent positions as required.

By way of example, acontemplated specific embodiment of the invention will now be described with reference to theaccompanying drawings. Thisembodiment takes the .form of an electrically-operated changing display indicator of the type in which an endless chain carries a series of display surfaces to be displayed one at a time. The indicator is constructed so that it may be assembled alongside and above and below other similar indicators to form a large composite indicator capable of indicatingy complex changing information. The indicator is arranged to be driven by a primary driving means (for example a driving electromotor) common to a plurality of indicators. The indicator includes a main framework, a clutch unit, a control unit, and the endless chain carrying the series of display surfaces. Fig. 1 of the drawings is a side View of the indicator illustrating how the main framework, the clutch unit, the control unit, and an endless chain carrying fourteen display surfaces are assembled together. To simplify the figure, most of the mechanism of the clutch and control units and many other details are omitted. Figs. 2 and 3 of the drawings are side and plan view respectively of the clutch unit, and Figs. 4 and 5 are side and underneath views respectively of the control unit. The main framework is designed to permit an endless chain having twice the length of the endless chain shown in Fig. 1, and carrying twenty-eight display surfaces instead of fourteen, to be used. Fig. 6 is a circuit diagram pertaining to the case where the endless chain and the display surfaces are as illustrated in Fig. 1, and shows the forms taken in this case by the code and certain other discs which are included in the control unit. Fig. 7 is a corresponding circuit diagram pertaining to the case where the endless chain carries twenty-eight display surfaces. The intention is to t the shorter endless chain, and the discs appropriate thereto, where the indicator is required to display the numerals l, 2, 3, 9, 0, and to t the longer endless chain, and the discs appropriate thereto, where the indicator is required to display the letters of a twenty-six letter alphabet.

Referring firstly to Fig. l, the main framework 1 of the indicator is broadly angle-shaped when viewed from the front or rear of the indicator. When viewed from the front (that is from the left as seen in Fig. 1), the main framework 1 is seen as having a vertical portion lying to the left of the clutch and control units, and as having a horizontal portion 2 lying underneath these units. Only the edge of the horizontal portion 2 is seen in Fig. l. The horizontal portion 2 serves to constitute a locating and protecting base for the indicator when the indicator is inserted in position as a unit of a large composite indicator. Over a small part of its length at the extreme rear of the indicator, the main framework 1 has no horizontal portion. A hole 3 in the vertical portion of the main framework, near the rear edge of this framework, provides a sonvenient finger-hold for use in inserting the indicator in position as a unit of a large composite indicator and withdrawing it from such position. A main mounting plate 4 of the clutch unit is secured to the vertical portion of the main framework 1 by four screws which engage four threaded bushes 5 forming part of the mounting plate 4. The apparatus of the clutch unit is carried by the mounting plate 4, and this apparatus includes a sprocket wheel 6 which engages the endless c hain 7. As illustrated, the endless chain 7 has seventy links and carries fourteen display surfaces 8. The endless chain 7 is shown occupying a display (stopping) position in which the particular display surface 9 is displayed. From the front of the indicator, the display surface 9 is seen as a rectangular surface bearing the appropriate representation. The sprocket wheel 6 has fifteen teeth, and therefore, since there are five teeth of the endless chain 7 per display surface, has to rotate one third of a revolution to change the indication from that given by one display -surface to that given by the next succeeding display surface. A notched wheel 10 with three equally-spaced notches moves with the sprocket wheel 6 and serves, as will be described later, to ensure that the endless chain 7 is only stopped in a stopping position. A main mounting plate 11 of the control unit is secured to the vertical portion of the main framework 1 by four screws which engage four threaded bushes 12 forming part of the mounting plate 11. The four screws pass through four slots 13 formed in four finger-like parts 14 of the vertical portion of the main framework 1. The slots provide for adjustment of the tightness of the endless chain 7, this chain being engaged at its rear by a sprocket wheel 15 forming part of the control unit and carried by the mounting plate 11. The sprocket wheel 15 has fifteen teeth, and therefore, since there are tive teeth of the endless chain 7 per display surface, is rotated one third of a revolution in respect of a change of indication from that given by one display surface to that given by the next succeeding display surface. The finger-like parts 14 provide for flush mounting of the control unit upon the main framework 1. The full frontto-back length of the main framework 1 is not shown in the gure. The part not shown, in the break at 16, includes four further finger-like parts 14 which are suitably situated (with reference to the sprocket wheel 6) to provide for the appropriate fixing of the mounting plate 11 in the case where the endless chain used has twice the length of the endless chain 7 illustrated (that is, where the endless chain has links instead of 70 links and carries 28 display surfaces instead of 14).

Referring now to Figs. 2 and 3, as has already been stated Fig. 2 shows a side view of the clutch unit and Fig. 3 shows a corresponding plan view. The main mounting plate 4 of the unit, the threaded bushes 5, the sprocket wheel 6, and the notched wheel 10 have previously been referred to in connection with Fig. 1. Permanently secured to the mounting plate 4 (for example by riveting) is a subsidiary metal mounting plate 17 which forms a shelf 18. The shelf 18 has a part 19 turned downwards, and carries a latch electromagnet 20. The latch electromagnet is secured to the shelf by two screws 21 which engage threaded holes in the yoke 22 of the latch electromagnet. A metal plate 23 secured to the yoke 22 carries the pivot 24 for the armature 25 of the latch electromagnet, and also carries a contact spring 26. The contact spring 26 is secured to the plate 23 in an insulated manner, and is tensioned so that it bears against a further thicker spring 27 when the latch electromagnet is not energised. The spring 27 is also insulated from the plate 23. The armature 25 is shown in its normal unoperated position, to which it is always urged by its restoring spring 28. One end of the spring 28 passes round a hook-shaped portion 31 of the armature 25, and the other end passes through a slot in a screw 32 which is screwed through the part 19 of the shelf 18. The armature 25 has an extension (shown partly broken away in Fig. 3) forming a latch 29. The latch 29 serves, by its engagement with the notched wheel 10, to locate and hold this wheel in its various stopping positions, and hence to locate and hold the endless chain in the various display positions. The latch 29 also serves, by its engagement with the notched wheel 10, mechanically to hold the armature 25 in its operated position whilst the endless chain is being driven between display positions. The armature 25 has a further extension 30 carrying a contact pip which makes contact with the contact pip on the contact spring 26 when the armature 25 is in its operated position. A terminal tag 33, secured by the nut 34 which secures the yoke 22 to the core of the latch electromagnet, serves as the terminal for the extension 30. A satisfactory electrical connection between the terminal tag 33 and the extension 30 is provided by a circuit through the yoke 22 and the pivot 24. The terminal tag 35 is the terminal of the Contact spring 26. The terminal tags 36 are the terminals for the latch electromagnet. The clutch unit includes an electromagnet clutch of known type. This clutch serves to couple the sprocket wheel 6 and the notched wheel 10 to a gear wheel 37. When the indicator is inserted in position as a unit of a large composite indicator, the

' indicator is to take place.

gear wheel 37 engages a pinion hired to a shaft which is continuously rotated by the relevant common primary driving means during periods in which setting of the The nature of the electromagnetic clutch employed does not concern the' present invention, and it is therefore unnecessary to illustrate and describe the details of its construction. It comprises a driving part constituted by a pot electromagnet 38 secured to the gear wheel 37, and a driven part constituted by a magnetic armature 39 secured to the sprocket wheel 6 and the notched wheel 10. The armature 39 is secured to the sprocket wheel 6 and the notched wheel 10 through the medium of spring members which serve to hold the armature 39 out of frictional driving engagement with the pot electromag'net 38 during periods in which this electromagnet is not energised. `During periods in which the pot electromagnet 38 is energised, the armature 39 is attracted into driving engagement with this electromagnet. The axle 4.0 on which both the assembly comprising the gear wheel 37 and the pot electromagnet 38, and the assembly comprising the sprocket wheel 6 and the notched wheel and the armature 39, rotate, is a fixed axle having one end fixed in the main mounting plate 4. The two assemblies just referred to are held in position on the axle 40 by "a clip 41. The arrangements for energising the pot electromagnet 38 comprise two Wipers 42 which engage two corresponding sliprings secured in a suitably insulated manner on that face of the gear wheel 37 which is remote from the pot electromagnet. The wipers 42 are secured to the mounting plate 4in an insulated manner, and have terminal tags 43 which in effect serve as the terminals of the pot electiomag'net 38. p i y Referring now to Figs. 4 and 5, as has already been stated Fig. 4 sho/ws a side view of the control Aunit and Fig. 5 shows a corresponding underneath view. The main mounting plate 11 of the unit, the threaded bushes 12, and the sprocket wheel have previously been referred to in connection with Fig. 1. Fixed to the sprocket wheel 15 so as to rotate with it is a geai wheel 44 which engages a pinion 45 (see 5). The axle 46 on which the assembly comprising the Vsprocket wheel 15 and the gear Vwheel 44 rotates is a xed axle having one end fixed in the main mounting plate 11. The assembly is heldin position on the axle 46 by a clip 47. The gear ratio between the gear wheel 44 and the V'pinion 45' is such that one third of a revolution of the gear wheel 44 produces one revolution of the pinion 4S. Fixed to the pinion 45 so as to rotate with it is the driving oi' pin wheel 4S (see Fig. 5`) of a vGeneva gear. The pin of the pin wheel 48 is shown at 49 in Fig. 5. The driven wheel 50 of the Geneva gear has seven slots 51, so that one revolution of the pin wheel 48 'produces one seventh of a revolution ofthe wheel S0. Fixed to the wheel 50 so as to rotate with it is a pinion 52 (see Fig. 5) which engages a gear wheel 53. The assembly comprising the wheel 50 and the pinion A"52 rotates on a fixed axle having one end fixed in the main mounting platelll. Fixed to the gear wheel 53 so as to rotate with it is the rotor 54 of a code' switching device. The axle 5S on which both 'the assembly comprising the pinion 45 and the 'pin wheel 4S of the Geneva gear', and the assembly Comprising the gear wheel 53 and the rotor 54, rotate, is axed axle having one end xed in the main mounting plate 11. The two assemblies just referred to are held in position on the axle 55 by a clip 56. The gear ratio between the pinion 52 and the gear wheel 53 is such that one revolution of the pinion 52 produces one quarter of a revolution of the gear wheel 53. From what has been said about gear ratios, it follows that one third of a revolution of the gear wheel 44 (that is, the movement of the gear Wheel 44 corresponding to a change of indication from the indication given by one display surface to the indicationg'iven by the next succeeding display surface) produces one twentyeighth of a revolution of the rotor s4. The rotor ncludes six conducting discs 57, 58, 59, 60, 61 and 62, which are in permanent electrical connection with one another through the medium of ve conducting spacers 63 (see Fig. 5). The six conducting discs and the ve conducting spacers 63 are suitably clamped together and insulated from the mounting plate 11. The gear wheel 53 and the rotor 54 are clamped together by an internal bearing member having an external nut-like portion 64. In the case where the endless chain has seventy links and carries fourteen display surfaces, the six conducting discs of the rotor have the forms shown in Fig. 6, discs 59, 60, 61 and 62 being code discs, disc 57 being a reset disc, and disc 5S being a feeder disc. In the case where the endless chain has 14) links and carries twenty eight display surfaces, the six conducting discs of the rotor have the forms shown in Fig. 7, discs 53, 59, 60, 61 and 62 being code discs, and disc 57 being a combined reset and feeder disc. Similar xed wipers 65, 66, 67, 68, 69 and 70 are associated with the conducting discs 57, 5S, 59, 60, 61 and 62 respectively. Each wiper is of the split type comprising two parts arranged to engage the two surfaces of the associated Conducting disc. The wiper assembly is secured to the main mounting plate 11 by several screws such as 71 (Fig. 5), and itselr` includes fixing screws 72 and 73 and clamping screws 74. The fixed wipers 65 to 7@ are suitably insulated from each other and from the mounting plate 11. ln the case where the endless chain has links and carries twenty-eight display surfaces and disc 57 is a combined reset and feeder disc, the disc 57 has associated with it, as illustrated in Fig. 4, a fixed feeder wiper 7S additional to the wiper 65. This feeder wiper 75 is suiciently broad at its wiping vend to bridge the single cut-away portion which the disc 57 has in this case. When provided, the feeder wiper 75 forms part of the same wiper assembly as the other wipers and is suitably insulated from the other wipers and from the mounting plate i1. The wipers have terminal tags 76.

Referring now to Fig. 6, this as has already'been stated is a circuit diagram pertaining to the case where the endless chain carries fourteen display surfaces. ln describing the operation of the indicator in this case, it will be assumed that the display surface which is displayed when the endless chain is occupying its normal position is a blank, and that the display surfaces which are displayed when the endless chain is at its first, second, third ninth, and tenth stopping positionsv from normal display the numerals 1, 2, 3, 9, and 0 respectively, and that the remaining display surfaces are further blanks. In the circuit diagram, the six conducting discs 57, 58, 59, 60, 61 and 62 of the rotor of the code switching device are shown occupying a normal position relative to the fixed wipers 65, 66, 67, 68, 69 and 70. Movement of the endless chain, whether for setting the chain to cause a particular numeral to be displayed or for resetting the chain to its normal position, is always in the direction which brings about clockwise movement, as seen in Fig. 4 and Fig. 6, of the rotor of the code switching device. In the case now being considered, since 'the endless chain has only fourteen stopping positions including the normal position, and since movement of the chain from one stopping position to the next succeeding stopping position only produces one twenty-eighth of a revolution of the rotor of the code switching device, one complete movement of the endless chain from its normal position through the different displays positions to its normal position only produces one half of a revolution of the rotor of the code switching device. As a consequence of this, the rotor of the code switching device has in effect two normal positions half a revolution apart, and is arranged, as will Vbe clear from a study of Fig. 6, to perform the same sequence of switching operations on movement through half'a revolution from either of these positions. A full movement of the rotor from one of its normal positions to 'the other normal position involves fourteen steps of the rotor, such steps being of course brought about by the Geneva gear. In the circuit diagram, the latch electromagnet 20 is shown connected between negative battery and the fixed wiper 66, and the pot electromagnet 38 of the electromagnetic 5 clutch and the make contact LMC of the latch electromagnet are shown connected in series between negative battery and positive battery. The make contact LMC is the Contact constituted by the extension 3i) (Fig. 2) of the armature of the latch electromagnet and the contact spring 26 (Fig. 2). Contact R is a contact which is closed to reset the endless chain to its normal position, and contacts W, X, Y and Z are code contacts which are closed in different combinations to set the endless chain to display the different numerals. The different combinations involved are as shown in the following table:

Table l Corresponding position from norm al Numeral to be displayed Code eontuot(s) closed A code signal signifying that a particular numeral is to be displayed is a four-element one, the first element determining whether code contact W is closed or open, the second element determining whether code contact X is closed or open, the third element determining whether code contact Y is closed or open, and the fourth element determining whether code contact Z is closed or open. Each of the conducting discs 57, 59, 60, 61 and 62 has portions cut away as shown, so that a through circuit between the disc and the associated fixed wiper only exists when the rotor of the switching device is occupying certain positions. The conducting discs which are in electrical contact with the respective fixed wipers when the rotor occupies its various positions are shown in the following table:

Table II 0 Conducting discs in electrical con o l 051mm of Rotor tact with respective fixed Wipers Normal 58 59 (i0 61 G2 First (from normal) 57 58 60 61 62 Secon 57 58 59 61 62 Third-.. 57 5s 6i 62 5o Fourth. 57 58 59 60 62 Fifth 57 5S 60 62 Sixth 57 5S 59 62 Seventh Eighth Ni11th 'lenth Elovent Twelfth In considering the operation of the indicator, it must be borne in mind that the conducting discs 57, 58, 59, 60, 61, and 62 are all in permanent electrical connection with one another through the medium of the five conducting spacers 63 (Fig. 5). The latch electromagnet 20 is in effect connected in a control circuit which has a code branch for each element of the code concerned. The control circuit code branch for the first element of the code comprises the code disc 59, the fixed wiper 67, and the code contact W. The control circuit code branch for the second element of the code comprises the code disc 60, the fixed wiper 68, and the 75 code contact X. The control cricuit code branch for the third element of the code comprises the code disc 61, the fixed wiper 69, and the code contact Y. The control circuit code branch for the fourth element of the code comprises the code disc 62, the fixed wiper "10, and the code contact Z. Upon the closing of one or more of the code contacts W, X, Y, and Z for the purpose of setting the endless chain from its normal position to the stopping position in which it displays the particular numeral signified by the code signal concerned, the latch electromagnet 20 is energised over one or more of the control circuit code branches. Upon such energisation of the latch electromagnet 20, the latch 29 (Fig. 2) is withdrawn from engagement with the notched wheel 10, and the latch electromagnet contact LMC (Fig. 6) is closed. The closing of contact LMC closes the circuit of the pot electromagnet 38 of the electromagnetic clutch, with the result that the sprocket wheel 6 (Fig. 2) and the notched wheel 10 are coupled to the relevant common primary driving means and are driven by this means. The arrangements are such that the energisation of the pot electromagnet 38 is maintained until the sprocket wheel 6 has driven the endless chain to the requisite stopping position. During periods in which the endless chain is moving between stopping positions, contact LMC is held closed independently of the condition of the latch electromagnet 20 by reason of the fact that the latch 29 (Fig. 2) cannot then enter a notch in the notched wheel 10. The Geneva gear (Figs. 4 and 5) is arranged so that stepping of the rotor of the code switching device takes place whilst contact LMC is thus held closed independently of the condition of the latch electromagnet 20. At any stopping position reached before the requisite stopping position is reached, the condition obtains that one or more of the four control circuit code branches are effective to energise the latch electromagnet 20. At the requisite stopping position, the condition obtains that none of the four control circuit code branches is effective to energise the latch electromagnet. Supposing, as a first example, that it has been signified by a code signal that the numeral 1 is to be displayed by the indicator in the case to which Fig. 6 pertains, then (see Table I) code contact W is closed whilst the endless chain is in its normal position. The latch electromagnet 20 is energised over the control circuit code branch comprising the code dise 59, the fixed wiper 67, and the code contact W. Contact LMC is closed and driving of the endless chain takes place. Whilst the chain is moving from its normal position to the next succeeding position in which the numeral 1 displayed, the Geneva gear steps the rotor of the code switching device to its first position from normal. When the rotor of the code switching device is in its first position from normal, the last-mentioned control circuit code branch is open at the code switching device (see Table Il). Thus, when the endless chain reaches the first position from normal, the condition obtains that none of the four control circuit code branches is effective to energise the latch electromagnet 20, so that the latch 29 (Fig. 2) enters the relevant notch in the toothed wheel 10 and contact LMC is opened. The endless chain is accordingly stopped at the stopping position at which the numeral 1 is displayed. Supposing, as a further example, that it has been signified by a code signal that the numeral 7 is to be displayed, then (see Table l) code contacts W, X, and Y are closed whilst the endless chain is in its normal position. As a result of this the latch electromagnet 20 is initially energised over the three control circuit code branches which include the three code discs 59, 6i), and 61. When the endless chain reaches the first position from normal, the two control circuit code branches which include the two code discs and 61 are closed at the code switching device (see Table II) and are effective to energise the latch electromagnet20, so that contact LMC is mainteaser normal, the two control circuit code branches which in` clude the 4two code discs '59 `and '60 are effective. At the iifth position from normal, the control circuit code branch which includes the code disc 60 is effective. At the sixth position from nor'inal, the` control circuit code branch which includes 'the code disc 59 is effective. At the seventh position from normal, the three control circuit codebranches which include the three code discs 59, 6i), and 61 are all open at the code switching device, so that the condition obtains that none of the four control circuit code branches is effective to energise the latch electromagnet 20. The endless chain is accordingly stopped at vthe stopping position at which the Vnumeral 7 is displayed. when the indicator has been setfto display a numeral, the subsequent opening of the code contacts closed to effect such` setting does not in `itself bring about any change of the setting; 4To reset the indicator to normal, the contact R is closed with all "the code contacts open, with the result that an energis'ing circuit for theY latch electromagnet is closed over the reset disc 57 and the xed wiper until the endlessvchain' nears its normal position. The exact location of the chain in its normal position is eifected by the action of the latch 29 (Fig. 2). l y

Referring now to Fig. 7, this as has already been stated is a circuit diagram pertaining to the case where the endless chain has "twice the length of the endless chain shown in Fig. l and carries twenty-eight display surfaces. In describingthe operation of Vthe indicator in this case, vit will be assumed that the display surface which is displayed when 'the endless chain is occupyingits normal position 4is ablank, and that the display surfaces which are displayed when the endless chain is at its rst, second, third, A. twentyfth, and twenty-sixth stopping positions from normal display 4the letters A, B, C, Y, and Z respectively,l and that the remaining display surface is a further blank. In the circuit diagram, the six conducting discs 57, 58, 59, 60, 61, and 62 of the rotor of the code switching device are shown occupying theirnorinal position relative to the xed wipers 65, 66, 67, 568, 69, and 70. Movement of the endless chain, whether fory setting the chain to cause a particular letter to be displayed or lfo'rresetting the chain to its normal position, is always in the direction which brings about clockwise movement, Aas seen in Fig. 7, of the rotor of the code switching device. In the case now being considered, since the endless chain has twenty-eight stopping positions including the normal position, and since movement ofthe chain from one stopping position to the next succeeding ystopping position produces one twenty-eighth of a revolution of the rotor of the code switching device, one complete movement of the endless chain from its normal position through the different display positions and back to its normal position produces one ievolution of the yrotor of the 'code switching device. lHence in this case the rotor of the code switching device has only one normal position. In

the circuit diagram, the latch electro-magnet 2,0 is shown connected between negative battery and the fixed yfeeder wiper 75 (see Fig. 4) associated with the combined resetand feeder disc- 57.` As has already been stated, the xed feedermw'iper 7S is 's'uticiently broad at its wiping end to bridge the single cut-away portion of the disc S7, so that this' wiper is always in l'Contact with the disc '57. The pot electromagnet 38 f the electromagnetic clutch and the maire contact LMC f the latch electromagnet are -connected asin the 'ca'se previously considered with reference te Fig. 6.

It should be noted that, Y

Contact R is a t 10 caract which is closed 'fo reset the endlessnehin te its herhaal position, and contacts P, Q, R, s, and T are code contacts which are closed in different coinbinations to set the endless chain to display the different letters. The dile'rnt combinations involved are as shown in ythe following table:

Table III Corre- Letter to be displayed Code Contact@ closed A code signal signifying that a particularrletter is to be displayed is a tive-element one, the iirst element determining whether code contact Pvisclosed or open, the second element determining whether code contact Q is closed or open, the third element determining whether code contact R is closed or openZV the fourth element determining whether code contact S is closed or open, and `the fifth elementdetermining whether code `contact T is closed or open. Each of the conducting discs 57, 58, y59, 60, 61 and 62 has portions cut away as shown, so that a through circuit between the disc andthe associated one of the iixed wipers 65, 66k, 67, 68, 6,9, and 70 only exists when the rotor o f the switching device is occupying certainpositions. The conducting discs which are in electricalcontact with the respective ones of wipers 65, 66, 67, 68, `69, and 70 when the rotor occupies its various positions are shown in the following table:

Table IV Position o'f rotor The latch electromagnet 20 is in effect connected in a control circuit which has a code branch for each element of the code concerned. The control circuit code branch for the first element of the code comprises the code disc 58, the fixed wiper 66, and the code contact P. The control circuit code branch for the second element of the code comprises the code disc 59, the fixed wiper 67, and the code Contact Q. The control circuit code branch for the third element of the code comprises the code disc 60, the fixed wiper 68, and the code contact R. The control circuit for the fourth element of the code cornprises the code disc 61, the fixed wiper 69, and the code contact S. The control circuit for the fifth element of the code comprises the code disc 62, the fixed wiper 70, and the code contact T. Upon the closing of one or more of the code contacts, P, Q, R, S, and T for the purpose of setting the endless chain from its normal position to the stopping position in which it displays the particular letter signified by the code signal concerned, the latch electromagnet 20 is energised over one or more of the control circuit code branches. The latch electromagnet contact LMC is consequently closed, with the result that the circuit of the pot electromagnet 38 of the electromagnetic clutch is closed. The setting of the indicator is controlled in a manner similar to that which has previously been described with reference to Fig. 6, the energisation of the pot electromagnet 38 being maintained until the sprocket wheel 6 (Fig. 2) has driven the endless chain to the requisite stopping position. At any stopping position reached before the requisite stopping position is reached, the condition obtains that one or more of the five control circuit code branches are effective to energise the latch electromagnet 20, whilst at the requisite stopping position the condition obtains that none of the five control circuit code branches is effective to energise the latch electromagnet. Supposing, by way of example, that it has been signified by a code signal that the letter W is to be displayed by the indicator in the case to which Fig. 7 pertains, then (see Table III) code contacts P, Q, R, and T are closed whilst the endless chain is in its normal position. In these circumstances, at each stopping position from normal up to and including the fifteenth position from normal, the control circuit code branch which comprises the code disc 62, the fixed wiper 70, and the code contact T is effective to energise the latch electromagnet (see Table IV), no matter Whether the other control circuit code branches are open or closed. At the sixteenth, seventeenth, eighteenth, and nineteenth stopping positions from normal, at least the control circuit code branch which comprises the code disc 60, the fixed wiper 68, and the code contact R is effective to energise the latch electromagnet. At the twentieth and twenty-first stopping positions from normal, at least the control circuit code branch which comprises the code disc 59, the fixed wiper 67, and the code contact Q is effective to energise the latch electromagnet. At the twenty-second stopping position from normal, the control circuit code branch which comprises the code disc 58, the fixed wiper 66, and the code contact P is effective to energise the latch electromagnet. At the twentythird stopping position from normal none of the control circuit code branches is effective to energise the latch electromagnet, and the endless chain is stopped to display the letter W. The closing of contact R with all the code contacts open effects the resetting of the indicator to normal as will be clear from the explanation of resetting given with reference to Fig. 6.

Although a common primary driving means has been referred to in the preceding description, it will of course be understood that an indicator may be provided with an individual driving electromotor if desired.

In order to provide for proper setting of an indicator according to the invention with some forms of code, it may be necessary to arrange the displays in a non-numerical and/or non-alphabetical order on the endless chain.

An indicator according to the invention may be a1'- ranged to be controlled by code signals previously recorded in the form of perforated tape.

What is claimed is:

l. In an electric selective signalling system employing multi-element code signals, a driven member having a normal position, electromagnetic means for bringing about continuous unidirectional setting movement of said driven member while said means is energized, an energizing winding of said electromagnetic means, a control circuit for said electromagnetic means connected between the two sides of a power supply circuit and having an unbranched portion containing said energizing winding and having a code branch for each element of the code employed and a single resetting branch, said code and resetting branches all being in parallel with one another, a code switching device, a rotor forming part of said code switching device and coupled to said driven member so as to be driven thereby, a conducting code disc forming part of said rotor for each said code branch and a single conducting reset disc forming part of said rotor, all said conducting discs being in permanent electrical connection with one an other and together constituting the commoning point of said unbranched portion and said code and resetting branches of said control circuit, a fixed wiper individual to each said conducting code disc for connecting the corresponding said code branch to said commoning point and a fixed wiper individual to said conducting reset disc for connecting said resetting branch to said commoning point, said conducting code and reset discs having portions cut away so that a through circuit between each of these discs and its wiper exists only when said rotor is occupying certain positions depending upon the disc, a fixed wiper cooperating with said rotor for continuously connecting said unbranched portion of said control circuit to said commoning point, means for closing, subject to the switching performed by said code switching device,

different combinations, corresponding to different code signals, of said code branches of said control circuit for bringing about the setting of said driven member from a normal position, and means for closing, subject to the switching performed by said code switching device, said resetting branch for bringing about the resetting of said driven member to a normal position.

2. An electrically-operated changing display indicator arranged for control by multi-element code signals, comprising a driven member having a normal position and a plurality of stopping positions at which different display surfaces are displayed, a primary driving means for producing for any requisite period a continuous unidirectional setting movement of said driven member, an electromagnetic clutch for coupling said driven member to said primary driving means, said electromagnetic clutch having an energizing winding bringing about such coupling while it is energized, a latch electromagnet having an armature permitting when said latch electromagnet is deenergized a latch to enter a notch in a notched wheel coupled to said driven member to stop the driven member at a stopping position, a contact closed by the armature of said latch electromagnet upon the energization of the latch electromagnet and held operated mechanically, whilst the driven member is moving between stopping positions, by reason of the engagement of the latch with the notched wheel, an energizing circuit for said energizing winding of said electromagnetic clutch closed while said contact is closed, an energizing winding of said latch electromagnet, a control circuit for said latch electromagnet connected between the two sides of a power supply circuit and having an unbranched portion containing said energizing winding of said latch electromagnet and having a code branch for each element of the code employed and a single resetting branch, said code and resetting branches all being in parallel with one another, a code switching device, a rotor forming part of said code switching de- 13 vice and coupled to said driven member so as to be driven thereby, a conducting code disc forming part of said rotor for each said code branch and a single conducting reset disc forming part of said rotor, all said conducting discs being in permanent electrical connection with one another and together constituting the comn moning point of said unbranched portion and said code and resetting branches of said control circuit, a fixed wiper individual to each said conducting code disc for connecting the corresponding said code branch to said commoning point and a lixed wiper individual to said conducting reset disc for connecting said resetting branch to said commoning point, said conducting code and reset discs having portions cut away so that a through circuit between each of these discs and its wiper exists only when said rotor is occupying certain positions depending upon the disc, a fixed wiper co-operating with said rotor for continuously connecting said unbranched portion of said control circuit to said commoning point, means for closing, subject to the switching performed by said code switching device, diierent combinations, corresponding to diierent code signals, of said code branches of said control circuit for bringing about the setting of said driven member from a normal position,

and means for closing, subject to the switching performed by said code switching device, said resetting branch for bringing about the resetting of said driven member to a normal position.

3. An electrically-operated changing display indicator as claimed in claim 2 comprising a coupling mechanism for producing a discontinuous movement of said rotor of said code switching device in respect of a continuous setting movement of said driven member.

4. An electrically-operated changing display indicator as claimed in claim 2 in which said fixed wiper for continuously connecting said unbranched portion of said control circuit to said commoning point wipes said reset disc, being suiciently broad at its wiping end to bridge the gap in this disc due to a portion being cut away.

References Cited in the tile of this patent UNITED STATES PATENTS 784,393 Grabosch Mar. 7, 1905 2,397,604 Hartley Apr. 2, 1946 2,535,954 Preston et al. Dec. 26, 1950 2,617,870 Kern Nov. 11, 1952 2,676,289 Wulfsberg et a1. Apr. 20, 1954 

